First off this is a bit like the old is my computer capable of running this thread with a twist. In the future (real soon within the next year) I will upgrading my computer to something simmilar to this.

New nehalem cpu and compatible mobo when they come out
4gigs of ram at least
1 dvd burner
2 new graphic cards in SLI, lets use the 8800 gtx for reference since its power hungry (not planning on that getting that card)
3 750-1 TB HD's
1 veloraptor HD

I was thinking of buying something along the lines of this as the power supply
http://www.newegg.com/Product/Prod [...] 6817703009

And this instead of adding another hard drive cage
http://www.newegg.com/Product/Prod [...] 6817994028

To my understanding power supplies only draw as much power as necessary, and I know that should be able to power everything. The problem is in a couple years I will keep adding more and more hard drives, so im wondering will it still run fine with 9 hard drives in it. Though I probably be using at most 3 hard drives at any given time (the veloraptor as the boot drive, and transfering data between 2 other hard drives)

So I guess the real question is does the other hard drives draw power when they are not in use?
And does everything draw power at full load when I boot up the computer, so will I have a problem with booting up the computer?
Should there be any other problems/concerns I didn't think of?

You could go with something like this:
http://www.newegg.com/Product/Prod [...] 6859105382

Build your self a gaming PC to go along with it.

Actually there is a reason why im avoiding the server idea, I don't usually need access to the other hard drives all that often except for retrieving the odd ball backups that used rarely, as well as tv shows after I get a TV tuner card, and various other stuff. So in general they will be lightly used, I guess I made it sound like I was building a server/gaming machine lol, my bad.

While my goal is a gaming machine with lots of storage and a good enough power supply, not an extreme overkill power supply.

A typicall HD would draw at most what? 15 W, so with 10 drives you'd be looking at 150 W tops the PCP&C PSU should handle it with ease.

Edit, I didn't saw the SLI part, seeing that the new GT 260/80 are power hogs I'd consider a kilowatt PSU.

Thats good to know, but will the hard drives still draw that power when not in use?

You are unlikely to end up with 9 drives, however, if you did, this power supply would handle it.
I am currently running a Q6600@3.2G, 8GB ram, 2 DVDRW, 6 internal SATA II drives, 2 external SATA II drives, HD 3870 Toxic, etc on an Enermax 600W PS. The case is a P182 with w 4x 120mm Scythe fans, plus the OCZ V2 cooler w 120mm fan.

Most MBs have at most 8 SATA ports, so I'm having difficulty imagining a machine with 10 drives.

Anyway, to answer the question about HDD drawing power when not in use:

http://www.extremetech.com/article [...] 9%2C00.asp

My favorite HDD these days is WD6400AAKS. Here are the numbers for it:
8.3W (average operating); 7.7W idle; 1.00W standby & sleep

A 1 TB WD SATA II drive draw 7.5W during read/write operations, in idle it draws 4W, and in standby or sleep it draws .97w.

http://www.wdc.com/en/products/pro [...] riveID=336

Agreed. Here's nVidia's official list of certified PSus for 9800GX2 SLI.
http://www.slizone.com/object/slizone_build_psu.html

The GTX 280 SLI will have exactly the same list, IMO, because GTX 280 and 9800GX2 have almost the same number of stream processors (240, 256 respectively). The list starts at 850W but most are 1000W or higher. Try something like the Corsair 1000HX or the Enermax Galaxy 1000W.

Yeah I give you it's unlikely I end up with 9 HD's, but I like looking at the worst case scenero of me needing that much in 3 years time, it probably take me quite a bit longer to fill that computer up with HD's. It was nice to find out all the info on how much power the hard drives pull and all the other information you guys gave me, so thanks everyone.

As for the comment on seeing a motherboard having that many sata slots, I already thought of that and was thinking of adding something like this (one of the first ones I pulled up, just to give an example), guess it would be called a sata controller/raid card, either way I need to look into these more as I lack any real knowledge on it.

http://www.newegg.com/Product/Prod [...] 6816102062

(added in)
Good point on the new video cards being power hogs, I look into a 1000watt PSU if I towards that route.

I say at least a PP&C 750 if not doing SLI with a dual GPU card. else, a 1kW PSU.

Cool, I didn't think of a SATA card...

OK, but seriously, in 3 years you'll be able to buy 2 TB disks for $300 or less. Nine of those means 18 TB .... I got 3 TB myself right now but less than half is used. I think you'll be OK even without a card like that.

You got me there, but I know the pack rat gene runs deep in my family so I know it will kick in somehow

In a couple of years your power supply will have lost up to, or more than 30% of its initial capacity. (depending on load and temperatures)

If you need 300w now, a 300w psu will work the first year or less.

It's better to go for a "bigger" psu early on, only for the purpose of maintaining stability over the years.

Something I noticed the hard way is that while you can happily run a 300w system on a 300w psu, in a while it'll start crashing as the output degrades.

With what you're planning, count high, cpu 70w, gpus 2x80w, hdds, 10x20w, mobo 30w = 460w + 30% = 598.

So go for a high grade, over 700w psu, for longevity.